Administration of microencapsulated Enterococcus faecium ABRIINW.N7 with fructo-oligosaccharides and fenugreek on the mortality of tilapia challenged with Streptococcus agalactiae

Abstract

We investigated the probiotic potential of a microencapsulated <i>Enterococcus faecium</i> ABRIINW.N7 for control of <i>Streptococcus agalactiae</i> infection in hybrid (<i>Oreochromis niloticus</i> × <i>Oreochromis mossambicus</i>) red tilapia. A two-phase experiment approach was completed in which <i>E. faecium</i> bacteria were propagated, from which a culture was isolated, identified using molecular techniques, and microencapsulated to produce a stable commercial fructooligosaccharide (FOS) and fenugreek (Fk) product of optimal concentration. The FOS and Fk products were assessed in a 90-days <i>in vivo</i> challenge study, in which red hybrid tilapia were allocated to one of five treatments: (1) No <i>Streptococcus agalactiae</i> (Sa) challenge (CON); (2) Sa challenge only (CON⁺); (3) Sa challenge in a free cell (Free Cell); (4) Sa challenge with 0.8% (w/v) Alginate; (5) Microencapsulated FOS and Fk. <i>In vitro</i> results showed high encapsulation efficiency (≥98.6 ± 0.7%) and acceptable viability of probiotic bacteria within the simulated fish digestive system and high stability of viable cells in all gel formulations (34 < SR% <63). <i>In vivo</i> challenges demonstrated that the FOS and Fk products could be used to control <i>S. agalactiae</i> infection in tilapia fish and represented a novel investigation using microencapsulation <i>E. faecium</i> as a probiotic diet for tilapia fish to control <i>S. agalactiae</i> infection and to lower fish mortality. It is recommended that local herbal gums such as 0.2% Persian gum and 0.4% Fk in combination with 0.8% alginate (Formulation 7) can be used as a suitable scaffold and an ideal matrix for the encapsulation of probiotics. These herbal gums as prebiotics are capable of promoting the growth of probiotic cells in the food environment and digestive tract.